The mother of a young Seattle woman who was murdered by her husband has described herself as a 'pit bull' in her six year campaign for justice after police refused to believe he was responsible.

In an episode of CBS's 48 Hours, titled 'Relentless,' Gael Schneider describes her heartbreak at learning her daughter, Nicole Pietz, 32, had been murdered in 2006 and the psychological warfare she waged against her daughter's husband David Pietz to expose the truth.

'I wasn't going to let her become another case in their files,' she says in the show due to air on Saturday November 2. 'I hate to think of myself as a pit bull, but I was.'

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Finding the truth: Gael Schneider, pictured, describes her heartbreak at learning her daughter, Nicole Pietz, 32, had been murdered in 2006 and the psychological warfare she waged against her daughter's husband David Pietz to expose the truth

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'She was my youngest daughter, and the absolute light of my life,' Schneider told 48 Hours. 'My beautiful daughter. My sweet girl. How anyone could hurt her is just – it's not feasible to me.'

Pietz told police that Nicole's had been addicted to prescribed painkillers after suffering medical issues but had kicked the habit. However, he said he suspected she'd been abusing medication again after being treated for a recent back injury.

Schneider knew her daughter's husband had more information he wasn't sharing but with few clues, the case went cold.

Killed: Nicole Pietz, 32, was found dead in February 2006. She is pictured with her husband, David Pietz

Emotional scene: Martin 'David' Pietz, right, is taken from court Monday in Seattle after a jury found him guilty of murdering his wife, as her sister, Tonia Zurcher, left, yells, 'You're going to hell, Pietz'

However, the desperate mother never let go. She always suspected Pietz was responsible for Nicole's murder and she vowed to uncover the truth.

She confronted Pietz at work, calling him a murderer in front of his colleagues, which prompted a restraining order.

Schneider left messages at his home and, she told 48 Hours, even left a blonde wig with fake blood on his doorstep.

She also urged investigators to reopen the case and, more than six years after Nicole was found dead, fresh detectives pieced together enough evidence to arrest David Pietz for her murder.

Earlier this month, a Washington state jury convicted him of second-degree murder in the death of his 32-year-old wife. Prosecutors said Pietz tried to cover up his wife's death by reporting her missing a week before her naked body was discovered.

Devastated: 'She was my youngest daughter, and the absolute light of my life,' Schneider told 48 Hours of Nicole, pictured left and right with her mom

Nicole's family wept openly in the courtroom when the guilty verdict was announced following a day and a half of deliberations.

Pietz was arrested in March by cold case detectives who had spent six years building a case against him based largely on circumstantial evidence.

Prosecutor Kristen Richardson later told the press that in the end, the case hinged on minor clues, including Pietz's alleged affairs with at least four different women and his wife's mouthguard, which she was wearing when her naked body was found in a wooded area near Burien, The Seattle Times reported.

During closing arguments, Richardson told the 12 members of the jury panel that Pietz had grown tired of being married to Nicole because of her reluctance to pursue a more adventurous sex life, and was 'cold and callous.’

In the course of the trial, four women testified they had sexual relations with Pietz while he was married to Nicole.

One of the husband's alleged lovers told the court in September that the 36-year-old defendant regularly spiked his wife's drinks with ecstasy to get her to take part in threesomes.

Pietz's defense lawyer said the man was wrongly accused and that prosecutors failed to establish a motive or come up with hard evidence such as DNA or witnesses to the crime.

'Dave Pietz isn't the first guy to step out on his spouse,' attorney David Allen told jurors. 'Is it a motive to kill his wife? He had bad boundaries; he's oversexed.'

The defense built its case on Nicole
Pietz's history of addiction to painkillers and claimed that the
32-year-old woman suffered a relapse after eight years of sobriety and
disappeared while out looking to score drugs.

However,
toxicology reports showed only trace amounts of prescription pills in
Nicole's system and no signs of recent drug abuse.

Pietz showed little emotion beyond beads of perspiration glistening on his brow when
the guilty verdict was announced.

Scene: Her body was found in a wooded area in 2006. Police said evidence suggested she had been killed at night - not in the day as Pietz suggested - as she still had her night mouth guard in

Cover? in 2006, Pietz had appeared on television beside Schneider pleading for information in the case

Emotions
ran high in the King County courtrhouse, where the victim's relatives
and friends sobbed with relief in reaction to the verdict.

Nicole
Pietz's sister Tonia Zurcher yelled out, 'You're going to burn in hell,
Pietz,' as he was led out of the courtroom following his conviction.

'I
just wanted justice for my daughter and we got it,' Gael Schneider, said at the hearing. 'These last 7 1/2 years have been torture for
us.'

Schneider then added, 'She'll never come back, we got justice for her, but I'll never get to hold her again,' the station KING5 reported.

For years, there were no charges
brought in connection with the murder - until police arrested Pietz
last year and charged him with second-degree murder thanks to advances in
technology.

Detectives were initially interested in Pietz as a suspect after learning that he was unhappy in his marriage and now they say they have built a case on circumstantial evidence.

Pietz, who had been married to his wife for four years, was finally arrested in March 2012 after DNA and phone GPS linked him to the crime scene, police said.

Loss: Investigators believe the couple was having marital problems and that Mr Pietz had cheated on his wife

Emotional: Earlier this week, Gael Schneider, Nicole Pietz's mother, unleashed an emotional rant when she came face-to-face with the accused killer in court

Investigators claimed there were
contradictions in his statements and he failed a lie detector test
before refusing to undergo a second.

Pietz told police that on January 27, 2006, he got home from work around
midnight and briefly said goodnight to his wife, who was already
sleeping, KOMO reported after his arrest.

The next morning he said he left for work at 8.30 a.m. without speaking to Nicole and had no contact with her throughout the day.

Pietz told police that he called 911 when he went straight to a planned
dinner with friends that night and his wife never arrived.

He claims she must have vanished as she headed to an Alcoholics Anonymous meeting that morning where she was going to celebrate eight years of sobriety. He claimed he believed she had fallen back into her old drug habit.

However, police said that forensic
tests - including undigested food in her stomach - showed that Nicole
had been killed around midnight on January 27.

When
her body was found, she was wearing a mouthguard she only wore at
night and her wedding ring was in cleaning solution in the bathroom;
friends said she only took it off at night to clean it.

Phone records also show her phone was allegedly used at her husband's workplace.

And
DNA evidence showed that Pietz's was the last person to drive her
car, which was found two weeks after her body in a parking lot near the
University of Washington.